FIELD OF THE INVENTION
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This disclosure relates to a stove, in particular a stove comprising an electrostatic precipitator (ESP).
BACKGROUND
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EP1967273 A2 discloses a stove comprising an ESP. A disadvantage of this stove is that it occupies a significant amount of space. The ESP is quite a bulky object that is positioned on top the stove. Hence, the stove would for example be unsuitable for relatively small living rooms.
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As known, ESPs have to be cleaned regularly. Due to a potential difference between a discharge electrode of the ESP, typically embodied as a metal pin, and a collection electrode, particles in the exhaust gases precipitate on a wall of the collection electrode. The particles that accumulate on the wall form an ash-like layer that becomes thicker over time. The ash-like layer comprises carbon and is therefore electrically conductive. While the ESP is in operation, the ash-like layer becomes thicker and approaches the discharge electrode. As a result, the risk of a electric discharge increases. Such electric discharge causes an electric current between the discharge electrode and collection electrode, which is undesired as it will alleviate the potential difference and prevent the ESP from operating. A problem of the stove as disclosed in
EP1967273 A2 is that its ESP is relatively difficult to clean.
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In light of the above, there is a need in the art for a stove that at least partially alleviates at least some of these problems.
SUMMARY
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Therefore, a stove is disclosed herein. The stove comprises an exhaust system for discharging exhaust gases from the stove. The exhaust system comprises an electrostatic precipitator, ESP. The ESP comprises a discharge electrode having a length extending along a longitudinal direction. The ESP also comprises a collection electrode extending along the longitudinal direction and comprising a wall that at least partially surrounds the discharge electrode. The wall defines a channel for accommodating a flow of exhaust gases along the longitudinal direction. The discharge electrode and collection electrode are configured to, when the ESP is in operation, cause particles in the exhaust gases to ionize and precipitate on the wall. The ESP further comprises an electrically insulating discharge electrode holder that holds the discharge electrode. The discharge electrode holder closes off the channel at one side of the channel for preventing a longitudinally directed flow of exhaust gases out of or into the channel at said one side of the channel. Further, the wall comprises an opening for letting exhaust gases out of or into the channel.
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This stove is advantageous in that it comprises an ESP. Therefore, fine particles can be filtered out of the exhaust gases and are therefore not discharged to the environment. When the ESP is in operation, typically, the collection electrode is grounded and a relatively high potential, for example several thousand Volts, is applied to the discharge electrode. The potential difference between the discharge electrode and collection electrode causes a corona discharge between the discharge electrode and collection electrode. Fine particles in the exhaust gases that travel in the longitudinal direction through the channel and through the corona discharge, ionize and precipitate on the collection electrode, in particular on the wall of the collection electrode that defines the channel. As such, fine particles in the exhaust gases are filtered out. The ESP thus reduces the environmental footprint of the stove.
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The disclosed stove is particularly advantageous in that it can be kept relatively compact, especially compact in the longitudinal direction. The ESP namely has a compact configuration where the discharge electrode holder closes off the channel that accommodates a flow of exhaust gases. As a result, the exhaust system of the stove does not need a further channel that lies outside of, yet in line with, the channel defined by the wall of the collection electrode. At the same time, the stove disclosed herein allows for configurations where particles in the exhaust gases can precipitate on the wall of the collection electrode along the entire length of the channel, even though the channel is closed off at one side. Even at the longitudinal position of the opening in the wall of the collection electrode, particles may precipitate on a part of the wall that sits opposite the opening, e.g. opposite in a transverse direction orthogonal to the longitudinal direction. Thus, the ESP disclosed herein can be made very compact in the longitudinal direction without significantly compromising its effectiveness.
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A further advantage of the discharge electrode holder closing off the channel at one side is that part of the discharge electrode holder is positioned outside of the channel accommodating the flow of exhaust gases. This part outside of the channel thus remains clean, which reduces the risk of a substantial electric current between discharge electrode and collection electrode and which eases the cleaning of the discharge electrode holder.
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Preferably, there is a plane that is orthogonal to the longitudinal direction and that intersects both the opening and the wall. This allows for particles in the exhaust gases to precipitate on a part of the wall that is present in that plane.
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The electrically insulating discharge electrode holder is preferably configured to prevent a substantial electric current between the discharge electrode and the collection electrode. The current between the discharge electrode and collection electrode due to the corona discharge is not a substantial electric current as referred to herein. Any electric current between the discharge electrode to the collection electrode that stops the corona discharge from happening may be understood as a substantial current referred to herein.
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The discharge electrode may be understood to specifically refer to a part from which corona discharge can occur towards the collection electrode. As such, the discharge electrode may for example be understood to refer to an exposed part of an electrode which exposed part is not covered by an insulating jacket.
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Preferably, the longitudinal direction is a substantially horizontal direction. This is advantageous because it prevents ash from falling out of the collection electrode into the stove, for example.
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In an embodiment, the collection electrode comprises a further opening at a side of the channel opposite said one side for letting exhaust gases into or, respectively, out of the channel. Preferably, the further opening allows for a longitudinally directed flow of exhaust gases into or, respectively, out of the channel. Alternatively, the further opening may be a second opening in the wall. This embodiment enables to cause a flow of exhaust gases through the channel in a convenient manner.
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In an embodiment, the collection electrode is a hollow cylinder extending in the longitudinal direction. In this embodiment, the wall is an interior wall of the hollow cylinder and the one side of the channel is at an end of the hollow cylinder. Further, in this embodiment, the discharge electrode holder closes off the cylinder at the end of the hollow cylinder for preventing a longitudinally directed flow of exhaust gases out of or into the hollow cylinder at the end of the hollow cylinder. Preferably, the discharge electrode is positioned on a longitudinal axis in the middle of the hollow cylinder.
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In this embodiment, the ESP may be understood to be a so-called tubular ESP, which are quite easy to clean and are quite efficient.
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In an embodiment, the hollow cylinder has a circular transverse cross section. This embodiment provides for an efficient ESP that is relatively easy to fabricate.
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Alternatively, the hollow cylinder has a transverse cross section having another shape than circular, such as a polygon, e.g. a simple, convex polygon, preferably a simple, convex, equilateral, cyclic polygon. The transverse cross section may have a square shape, for example, or a pentagon shape, or any other polygon shape.
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In an embodiment, the discharge electrode is a pin, preferably a metal pin, extending in the longitudinal direction.
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In an embodiment, the opening in the wall sits adjacent the discharge electrode holder. This embodiment is beneficial as it ensures that the flow of exhaust gases flow substantially all the way to (or from) said one side of the channel. Herewith, the efficiency of the ESP is increased.
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In an embodiment, the opening in the wall sits at the one side of the channel that is closed off by the discharge electrode holder.
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In an embodiment, at least part of the discharge electrode holder extends, along the longitudinal direction, into the channel. This embodiment is advantageous because it allows for an even more compact configuration of the ESP.
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In an embodiment, at least part of the discharge electrode holder extends, along the longitudinal direction, into the channel while leaving a space in a transverse direction between the wall and itself, wherein the transverse direction is orthogonal to the longitudinal direction.
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This embodiment is highly advantageous in that it provides for a configuration in which less particles will accumulate at the one side of the channel, in particular for a configuration in which less particles will accumulate on the discharge electrode holder at said one side of the channel.
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Since the discharge electrode holder closes off the channel at said one side of the channel and prevents a longitudinally directed flow out of or into the channel, the longitudinally travelling exhaust gases tend to flow against the discharge electrode holder to some extent. As a result, particles may precipitate on the electrically insulating electrode holder, which is undesired, as these particles, which comprise carbon, may form an electrically conductive layer, which may accommodate a substantial electric current between discharge electrode and collection electrode. As we know, such current is detrimental to the operation of the ESP.
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The inventor has found that, especially in the context of a channel that is closed off by an electrode holder as described herein, the problem of particles accumulating on the electrode holder is at least partially alleviated by having at least part of the electrode holder extend into the channel while leaving a space in the transverse direction between the wall and itself. This at least part influences the local flow of exhaust gases in such manner that less particles precipitate on the electrode holder. The at least part of the discharge electrode holder may cause the flow of exhaust gases to be more parallel to the shape of the electrode holder and/or to cause a more turbulent flow along the discharge electrode holder in the channel, such that less particles precipitate on the electrode holder itself. As a result, the discharge electrode holder does not have to be cleaned that often.
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In an embodiment, the at least part of the discharge holder that extends into the channel has a shape for reducing the amount of particles that precipitate on the at least part of the discharge electrode holder.
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In an embodiment, in the channel, a transverse cross section of the discharge electrode holder varies along the longitudinal direction.
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Such variation of the transverse cross section along the longitudinal direction even more strongly reduces the amount of particles precipitating on the electrode holder.
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As referred to herein, the transverse cross section of the discharge electrode holder is the intersection between the discharge electrode holder and a plane orthogonal to the longitudinal direction. For different longitudinal positions of the plane, the transverse cross section of the electrode holder may thus be different.
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In an embodiment, the discharge electrode holder extends to a position in the channel, and the discharge electrode holder's transverse cross section at said position is narrower than the discharge electrode holder's transverse cross section at the one side of the channel.
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The electrode holder may for example widen as it comes closer to the side of the channel. This embodiment even more strongly reduces the amount of particles precipitating on the electrode holder.
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In an embodiment, the discharge electrode holder's transverse cross section gradually widens closer to the one side of the channel.
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This embodiment is advantageous in that the discharge electrode holder has a sloped surface on which particles don't tend to precipitate.
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Preferably, the discharge electrode holder's transverse cross section gradually widens over more than 50% of the distance between the position in the channel and the one side of the channel, more preferably widens over more than 75% of this distance.
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In an embodiment, the electrode discharge holder has a conical shape and/or a paraboloid shape and/or hyperboloid shape and/or spherical shape.
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In an embodiment, the discharge electrode is releasably attached to the discharge electrode holder. This embodiment is advantageous in that it allows to take out and clean the discharge electrode holder without having to dismount the discharge electrode holder. The inventor has found that if the discharge electrode is cleaned periodically, which can be performed very easily in this embodiment, the electrode holder needs to be cleaned less often.
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In an embodiment, the stove comprises a combustion chamber, and the ESP is positioned lower than the combustion chamber of the stove, preferably beneath the combustion chamber. This embodiment effectively uses the space that is typically present below the combustion chamber. The combustion chamber is often positioned at a certain height so that the fire is clearly visible. By installing the ESP beneath the combustion chamber, the stove as a whole can be kept quite compact.
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In an embodiment, the stove is a pellet stove. This embodiment is advantageous because pellet stove are known to have a more efficient combustion than non-pellet stoves.
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In an embodiment, the discharge electrode holder comprises ceramic and/or porcelain. These materials have been found to be quite suitable for the electrode holder as they are electrically insulating and can withstand high temperatures. Preferably, the discharge electrode holder essentially consists of ceramic and/or porcelain.
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In an embodiment, the discharge electrode holder is releasably attached to the stove, and the collection electrode becomes accessible for cleaning the wall of the collection electrode when the discharge electrode holder holding the discharge electrode is detached from the stove.
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This embodiment is advantageous in that it allows for easily removing the ash-like layer that forms over time on the wall of the collection electrode.
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Preferably, the discharge electrode holder is positioned on a front side of the stove.
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In an embodiment, the ESP comprises a plurality of discharge electrodes and a plurality of collection electrodes. In this embodiment, each collection electrode comprises a wall that at least partially surrounds a discharge electrode out of the plurality of discharge electrodes, which discharge electrode has a length extending along a respective longitudinal direction, wherein the wall of the collection electrode in question defines a channel for accommodating a flow of exhaust gases along the respective longitudinal direction. Further, each collection electrode is configured to, together with the discharge electrode that it at least partially surrounds, cause particles in the exhaust gases to ionize and precipitate on the wall of the collection electrode in question when the ESP is in operation, the wall of the collection electrode in question comprising an opening for letting exhaust gases into or out of channel. In this embodiment, the stove further comprises a plurality of electrically insulating discharge electrode holders holding the plurality of discharge electrodes.
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This embodiment is advantageous in that it comprises a plurality of channels defined by the respective walls of the respective collection electrodes. The plurality of channels increase the capacity of the ESP.
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Preferably, of each collection electrode, the wall at least partially surrounds one and only one discharge electrode.
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Each discharge electrode and collection electrode pair may be understood to have its own longitudinal direction. In other words, the discharge electrodes out of the plurality of discharge electrodes are not necessarily parallel to each other and the collection electrodes out of the plurality of collection electrodes are not necessarily parallel to each other. However, in a preferred embodiment, the collection electrodes are parallel to each other and the discharge electrodes are also parallel to each other.
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Preferably, each discharge electrode holder closes off one and only one channel of one and only one collection electrode out of the plurality of collection electrodes at a side of the channel in question for preventing a longitudinally directed flow of exhaust gases out of or into the channel in question at that side.
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Preferably, each discharge electrode holder out of the plurality of discharge electrode holders is configured to hold one and only one discharge electrode out of the plurality of discharge electrodes.
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In an embodiment, each discharge electrode holder is releasably attached to the stove, and each collection electrode becomes accessible for cleaning the wall of the collection electrode when the plurality of electrically insulating discharge electrode holders holding the plurality of discharge electrodes is detached from the stove. In this embodiment, the discharge electrode holders out of the plurality of discharge electrode holders are mechanically connected to each other so that the discharge electrode holders are detachable from the stove all at once.
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A second distinct aspect of this disclosure relates to an electrostatic precipitator, ESP, that comprises a discharge electrode having a length extending along a longitudinal direction. The ESP also comprises a collection electrode extending along the longitudinal direction and comprising a wall that at least partially surrounds the discharge electrode. The wall defines a channel for accommodating a flow of exhaust gases along the longitudinal direction. The discharge electrode and collection electrode are configured to, when the ESP is in operation, cause particles in the exhaust gases to ionize and precipitate on the wall. The ESP further comprises an electrically insulating discharge electrode holder that holds the discharge electrode. The discharge electrode holder closes off the channel at one side of the channel for preventing a longitudinally directed flow of exhaust gases out of or into the channel at said one side of the channel. Further, the wall comprises an opening for letting exhaust gases out of or into the channel. Thus, in this aspect, the ESP is not necessarily installed in a stove nor is it necessarily part of an exhaust system. In this aspect, the ESP may be any of the ESPs disclosed herein and/or may have any feature of any ESP disclosed herein.
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A third distinct aspect of this disclosure relates to an electrostatic precipitator, ESP, that comprises a discharge electrode having a length extending along a longitudinal direction. The ESP also comprises a collection electrode extending along the longitudinal direction and comprising a wall that at least partially surrounds the discharge electrode. The wall defines a channel for accommodating a flow of exhaust gases along the longitudinal direction. The discharge electrode and collection electrode are configured to, when the ESP is in operation, cause particles in the exhaust gases to ionize and precipitate on the wall. The ESP further comprises an electrically insulating discharge electrode holder that holds the discharge electrode. Further, at least part of the discharge electrode holder extends, along the longitudinal direction, into the channel while leaving a space in a transverse direction between the wall and itself, wherein the transverse direction is orthogonal to the longitudinal direction. Also, in the channel, a transverse cross section of the discharge electrode holder varies along the longitudinal direction. Thus, in this third aspect, the discharge electrode holder does not necessarily close off the channel at one side of the channel for preventing a longitudinally directed flow of exhaust gases out of or into the channel at said one side of the channel and the wall does not necessarily comprise an opening for letting exhaust gases out of or into the channel. In this third aspect, the ESP may be any of the ESPs disclosed herein and/or may have any feature of any ESP disclosed herein.
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This third aspect is advantageous in that the varying cross section reduces the amount of particles that precipitates on the electrode holder.
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In an embodiment of the third distinct aspect, the discharge electrode holder extends to a position in the channel, wherein the discharge electrode holder's transverse cross section at said position is narrower than the discharge electrode holder's transverse cross section at the one side of the channel.
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In an embodiment of the third aspect, the at least part of the discharge holder that extends into the channel has a shape for reducing the amount of particles that precipitate on the at least part of the discharge electrode holder.
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In an embodiment of the third distinct aspect, the discharge electrode holder's transverse cross section gradually widens closer to the one side of the channel.
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A fourth distinct aspect of this disclosure relates to an electrostatic precipitator, ESP, that comprises a discharge electrode having a length extending along a longitudinal direction. The ESP also comprises a collection electrode extending along the longitudinal direction and comprising a wall that at least partially surrounds the discharge electrode. The wall defines a channel for accommodating a flow of exhaust gases along the longitudinal direction. The discharge electrode and collection electrode are configured to, when the ESP is in operation, cause particles in the exhaust gases to ionize and precipitate on the wall. The ESP further comprises an electrically insulating discharge electrode holder that holds the discharge electrode. In this aspect, the discharge electrode is releasably attached to the discharge electrode holder. Thus, in this fourth aspect, the discharge electrode holder does not necessarily close off the channel at one side of the channel for preventing a longitudinally directed flow of exhaust gases out of or into the channel at said one side of the channel and the wall does not necessarily comprise an opening for letting exhaust gases out of or into the channel. In this fourth aspect, the ESP may be any of the ESPs disclosed herein and/or may have any feature of any ESP disclosed herein.
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This fourth aspect is advantageous in that it allows the discharge electrodes to be cleaned easily and separately from the discharge electrode holders.
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A fifth distinct aspect an electrostatic precipitator, ESP, that comprises a discharge electrode having a length extending along a longitudinal direction. The ESP also comprises a collection electrode extending along the longitudinal direction and comprising a wall that at least partially surrounds the discharge electrode. The wall defines a channel for accommodating a flow of exhaust gases along the longitudinal direction. The discharge electrode and collection electrode are configured to, when the ESP is in operation, cause particles in the exhaust gases to ionize and precipitate on the wall. The ESP further comprises an electrically insulating discharge electrode holder that holds the discharge electrode. In this fifth aspect, the discharge electrode holder is releasably attached to the stove, and the collection electrode becomes accessible for cleaning the wall of the collection electrode when the discharge electrode holder holding the discharge electrode is detached from the stove. Thus, in this fifth aspect, the discharge electrode holder does not necessarily close off the channel at one side of the channel for preventing a longitudinally directed flow of exhaust gases out of or into the channel at said one side of the channel and the wall does not necessarily comprise an opening for letting exhaust gases out of or into the channel. In this fifth aspect, the ESP may be any of the ESPs disclosed herein and/or may have any feature of any ESP disclosed herein. For example, the discharge electrode holders may be positioned at the front side of the stove.
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This fifth aspect is advantageous in that it allows to clean the collection electrodes of the ESP in a very simple manner.
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In an embodiment of this fifth aspect, the ESP comprises a plurality of discharge electrodes and a plurality of collection electrodes, and each collection electrode comprises a wall that at least partially surrounds a discharge electrode out of the plurality of discharge electrodes, which discharge electrode has a length extending along a respective longitudinal direction, wherein the wall of the collection electrode in question defines a channel for accommodating a flow of exhaust gases along the respective longitudinal direction. In this embodiment, each collection electrode is configured to, together with the discharge electrode that it at least partially surrounds, cause particles in the exhaust gases to ionize and precipitate on the wall of the collection electrode in question when the ESP is in operation. In this embodiment, the stove further comprises a plurality of electrically insulating discharge electrode holders holding the plurality of discharge electrodes. Each discharge electrode holder is releasably attached to the stove, and each collection electrode becomes accessible for cleaning the wall of the collection electrode when the plurality of electrically insulating discharge electrode holders holding the plurality of discharge electrodes is detached from the stove. Further, preferably, the discharge electrode holders out of the plurality of discharge electrode holders are mechanically connected to each other so that the discharge electrode holders are detachable from the stove all at once.
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Elements and aspects discussed for or in relation with a particular embodiment may be suitably combined with elements and aspects of other embodiments, unless explicitly stated otherwise. Embodiments of the present invention will be further illustrated with reference to the attached drawings, which schematically will show embodiments according to the invention. It will be understood that the present invention is not in any way restricted to these specific embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
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Aspects of the invention will be explained in greater detail by reference to exemplary embodiments shown in the drawings, in which:
- FIGs. 1A, 1B and 1C illustrate a stove according to an emboidiment;
- FIG. 2A shows an ESP according to an embodiment;
- FIG. 2B illustrates how, according to an embodiment, the discharge electrodes are releasably attached to the collection electrodes;
- FIG. 3 is an explode view of the ESP of figure 2A;
- FIG. 4A is a front view of a stove according to an embodiment;
- FIG. 4B is a cross section of the stove shown in FIG. 4A;
- FIG. 4C is a detail of FIG. 4B;
- FIG. 5A is a perspective view on the collection electrodes of the ESP of figure 2A from a back view;
- FIG. 5B is a perspective view on the collection electrodes of the ESP of figure 2A from a bottom, back view;
- FIG. 5C is the same as FIG. 5A only with a part cutaway;
- FIG. 5D is the same as FIG. 5C only also showing the discharge electrodes;
- FIG. 6 shows different views of the ESP shown in FIG. 2A;
- FIG. 7 shows a discharge electrode holder in more detail;
- FIG. 8 shows a cross section B-B of the ESP indicated in FIG. 6;
- FIG. 9A shows a discharge electrode holder holding a discharge electrode according to an embodiment, in two different perspective views;
- FIG. 9B shows in more detail how the discharge electrode holder holds the discharge electrode according to an embodiment.
DETAILED DESCRIPTION OF THE DRAWINGS
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In the figures, identical reference numbers indicate identical or similar elements. It should be appreciated that although the figures show an embodiment in which the ESP comprises four collection electrodes and four discharge electrodes, the ESP as disclosed herein may also be embodied having another number of collection electrodes and discharge electrodes, for example having one and only one collection electrode and one and only one discharge electrode.
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Figure 1 illustrates a stove 2 according to an embodiment. The stove 2 comprises a combustion chamber 4 where some type of fuel, such as pellets, are burnt in order to generate heat and warm up the area surrounding the stove 2. The stove comprises an exhaust system (not indicated) that discharges the exhaust gases from the stove. Typically, the exhaust gases, once they have left the stove 2, are guided to outside of the building in which the stove 2 is installed, for example through a pipe through an outer wall or roof of the building. The exhaust system of the stove 2 comprises an electrostatic precipitator 6 (ESP). The exhaust gases will pass through the ESP 6 before being discharged from the stove 2. The ESP filters out particles out of the exhaust gases and thus significantly reduce the environmental impact of the stove 2. In the depicted embodiment, the ESP 6 is positioned beneath the combustion chamber 4 (see figure 1B), because this advantageously uses the space that is typically present below a stove's combustion chamber 4 and provides for a compact design of the stove 2 as a whole. However, the ESP may be positioned elsewhere on the stove 2, such as on top of the stove 2.
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Figure 1C shows that the ESP comprises element 8 and element 10. Elements 8 and 10 are shown in more detail in figures 2A and 2B. Element 8 comprises collection electrodes 12a, 12b, 12c, 12d of the ESP 6, and element 10 comprises discharge electrodes 16a, 16b, 16c, 16d of the ESP 6, and discharge electrode holders 14a, 14b, 14c, 14d of the ESP 6. In element 10, the discharge electrode holders 14a, 14b, 14c, 14d are mounted between two plates 26a, 26b and clamped therebetween. Each of the discharge electrodes 16a, 16b, 16c, 16d has a length that extends along a longitudinal direction. In the figures, each discharge electrode extends in a direction parallel to the indicated z-axis. Each of the collection electrodes 12a, 12b, 12c, 12d also extends in a direction parallel to the indicated z-axis. Each collection electrode 12a, 12b, 12c, 12d comprises an inner wall 18a, 18b, 18c, 18d, as indicated in figure 5A and 5C. Each inner wall 18a, 18b, 18c, 18d defines a channel for accommodating a flow of exhaust gases along a direction parallel to the z-axis. In the assembled state of the ESP, shown in figure 2A, the discharge electrodes 12a, 12b, 12c, 12d are respectively positioned within collection electrodes 12a, 12b, 12c, 12d and each wall 18a, 18b, 18c, 18d at least partially surrounds a discharge electrode. Each pair of discharge electrode and collection electrode is configured to, when the ESP is in operation, cause particles in the exhaust gases to ionize and precipitate on the wall of the collection electrode thus forming an ash-like layer on the wall.
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The electrically insulating discharge electrode holders 14a, 14b, 14c, 14d respectively hold the discharge electrodes 12a, 12b, 12c, 12d. In assembled state of the ESP (figure 2A), each discharge electrode holder 14a, 14b, 14c, 14d closes off the channel as defined by the collection electrode wall at one side of the channel for preventing a flow of exhaust gases in a direction parallel to the indicated z-axis out of or into the channel at said one side of the channel. Each wall 18a, 18b, 18c, 18d comprises an opening 20a, 20b, 20c, 20d for letting exhaust gases out of or into the channel.
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Figure 2B illustrates that element 10 may be releasably attached to element 8. If element 8 is attached to the stove 2, then element 10 being releasably attached to element 8 may be understood as element 10 being releasably attached to the stove 2. In principle, element 8 will remain attached to the stove because de-attaching it from the stove 2 is not required for cleaning the ESP. Element 10 may be releasably attached to element 8 and therefore to the stove 2 by means of bolts. For example, plate 26b may comprise flaps 27a and 27b each having a screw clearance hole that allows to attach plate 26b to plate 30 of element 8 by means of bolts 29a and 29b. In assembled state, plate 26b is airtight attached to plate 30 so that no exhaust gases can escape the system by flowing between the plates 26b and 30. To this end, plate 36a may comprise around each hole 36 (indicated in figure 3) a heat resistive sealing ring (not shown), for example a high temperature resistant silicone O-ring.
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Figure 3 shows an exploded view of element 10 and shows that the discharge electrode holders 14 are mounted between two plates 26a and 26b that are attached to each other by means of a plurality of bolts 28a - 28h. Plate 26a comprises holes 32a, 32b, 32c, 32d that, in assembled state of element 10, allow to electrically connect a voltage source to the discharge electrodes. Further, plate 26b also comprises holes 34a through which, in assembled state of element 10, the discharge electrodes extend. The collection electrodes 12a, 12b, 12c, 12d are attached to a plate that also comprises holes 36a through which the discharge electrodes extend when the ESP is in assembled state.
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Thus, in the depicted embodiment, the discharge electrode holders 14a, 14b, 14c, 14d are mechanically connected to each other so that the discharge electrode holders are detachable from the stove 2 all at once. The ESP disclosed herein, in particular the inner walls of the collection electrodes 12a, 12b, 12c, 12d, can be cleaned in a very straightforward manner. This only requires to take out element 10 from the stove as illustrated in figure 1C, herewith detaching, in one go, all discharge electrode holders 14 holding discharge electrodes 16. As a result, the collection electrodes 12 become accessible. For example, a vacuum can be used to suck up the particles that have precipitated on the inner walls of the collection electrodes 12a, 12b, 12c, 12d. This cleaning process does not require the collection electrodes to be removed from the stove 2.
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Figures 4A, 4B, 4C illustrate a possible flow of exhaust gases by means of the thick arrows. Figure 4A is a front view of the stove 2, figure 4B is a cross section along A-A as indicated in figure 4A, and figure 4C is a detail of figure 4B. The exhaust gases in the combustion chamber 4 rise and are guided downwards through duct 22 and guided into the channel as defined by collection electrode 12, in particular as defined by collection electrode's 12 inner wall. The exhaust gases enter the channel via opening 21 (see figure 5A). The stove 2 may comprise one or more fans for actively causing the exhaust gases to flow through pipe 22 and through the ESP. The exhaust gases then flow in the +z-direction through the collection electrodes 12. The exhaust gases cannot exit the channel defined by the collection electrode 12 at the side of the channel where the discharge electrode holder 14 is, because the discharge electrode holder 14 closes off the channel. Because the discharge electrode holder 14 closes off the channel at one side, there is no flow of exhaust gases directed along the z-axis entering or exiting the channel at that side. Instead, the exhaust gases exit the channel through opening 20. Thereafter, the filtered exhaust gases enter exhaust gas drain 24 (also indicated in figure 1C) via which they are disposed from the stove 2.
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Figure 5A shows element 8 comprising the four collection electrodes from a back view. The inner walls 18a, 18b, 18c, 18d are indicated. Figure 5A clearly shows that each collection electrode comprises an opening 21 at the side that is opposite the side of the channel where the opening 20 is.
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Figure 5B shows element 8 from yet another viewpoint.
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Figures 5C shows element 8 from the back view with part of element 8 being cut away to better show the interior of one of the collection electrodes, in particular collection electrode wall 18d.
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Figure 5D shows the ESP in assembled state from a back view with part of the ESP being cut away to better show how the discharge electrode 16d is positioned in collection electrode 12d.
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Figure 6 shows the ESP in assembled state as seen respectively from a top view, front view, bottom view, back view, and a right side view.
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Figure 7 shows cross section C-C as indicated in figure 6, and a detail of this cross section.
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Figure 8 shows cross section B-B as indicated in figure 6. In the embodiment depicted in the figures, the collection electrode is a hollow cylinder that extends in a direction parallel to the z-axis having a circular transverse cross section with radius R. The transverse cross section is an intersection of the hollow cylinder with a plane that is parallel to the xy-plane. The discharge electrode 16 would typically be a metal pin that is positioned, as viewed in the z-direction, in the middle of the cylinder.
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In the embodiment depicted in the figures, there is a plane P that is parallel to the xy-plane and that intersects both the opening 20 and the wall 18. Note that particles in the exhaust gases may still precipitate on the part 19 of wall 18, wherein the part 19 consists of all points on wall 18 for which it holds that a plane that is parallel to the xy-plane, i.e. orthogonal to the direction in which the discharge electrode and collection electrode extend, and that intersects the point in question also intersects opening 20. Note that plane P also intersects the discharge electrode holder, because the discharge electrode holder extends into the channel to some extent.
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In the channel, the transverse cross section of the discharge electrode holder varies along the longitudinal direction (z-direction). Indeed, as indicated, at a first position along the z-axis, the discharge electrode holder has a width W1, whereas at a second position closer to the end of the channel, the discharge electrode holder has a width W2 that is greater than W1.
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Figure 9A shows the discharge electrode holder 14 holding the discharge electrode 16. Figure 9B is an exploded view showing in more detail how the discharge electrode holder holds the discharge electrode 16. The discharge electrode 16, in this case a metal pin, is clamped into an elongated part of a tube 42. In the depicted embodiment, the discharge electrode holder 14 is configured to hold the discharge electrode in that it is configured to hold the tube 42. The tube can namely be mounted, preferably releasably mounted, in the discharge electrode holder 14.
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The tube 42 comprises a head that comprises a slot. Once an electrical wire 46 with jacket has been placed in the slot as shown, a screw 40 may be screwed into tube 42. The relatively sharp tip of the screw 40 will then pierce the jacket of the electrical wire and establish an electrical connection with the metal wire within the jacket. As a result, since the screw 40, tube 42 and pin electrode 16 are electrically conductive and electrically connected to each other, the discharge electrode 16 will receive the same potential as the electrical wire 46. When the ESP is in operation, the discharge electrode 16 may for example be kept at a potential of 15.000 V, while the collection electrode is connected to ground. Note that plates 30, 26a and 26b, since they are in contact with the collection electrodes, will also be connected to ground. The electrically insulating discharge electrode holders 14 serve to prevent electrical current between the discharge electrode 16 and any of plate 26a, plate 26b, plate 30, collection electrodes 12a, 12b, 12c, 12d. Such electrical current would alleviate the potential difference between collection electrode and discharge electrode, which would interrupt the functioning of the ESP. The discharge electrode holder 14 for example essentially consists of ceramic or porcelain.
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Preferably, the assembly of the screw 40, tube 42 and the discharge electrode is releasably attached to the discharge electrode holder 14 so that the discharge electrode 16 can be taken out of the collection electrode 12 for cleaning purposes without having to detach the discharge electrode holder from the stove.